standand error of curve fitting

[ddffrreeasd]

When I use the NonLinearFit function to fit a curve with the initial guess of coefficient, it returns the best coefficient array. But how can I know the standard error of this results? I mean the error of the so-called best coefficients.
Thank you very much

[JuanCarlos]

Hi,

Probably the most common way to evaluate how good was the approximation is to calcualte the RMS value of the error; basically subtracting the two waveforms and calculating the RMS of that array of differences. You can use CVI's RMS functions to do this. I hope this helps.

Juan Carlos
N.I.

[computing_marmot]

I use the Non-Linear Fit function and, as foreseen in the function description, I enter an initial guess of the coefficients I expect in return.

Then I'm faced to several problems: according to the value of the initial guess entered, the best given coefficients returned by the function vary a lot. As I don't really know which could be a good initial guess, it is a real problem.

Moreover, when I change the initial guess with the "best value" returned once by the program, the value doesn't stand constant, but decreases.

I have tried to enter a large range of initial guesses, and I've noted that when the initial guess is too far from the possible result, the function returns the same values as entered in the initial guess. It seems even not to calculate the coefficients, and just returning the first guess values. I don't understand why it happens, because in the definition of the function, it is specified that if the system doesn't find a solution a the end of the maximum iteration number, it returns an exception error.

Could you help me with these problems, please?

Thanks in advance.